Heat exchanger

ABSTRACT

Thermal expansion of U-shaped tubes is permitted to prevent damage to it. A heat exchanger includes a casing having a first fluid inlet provided at one end thereof and a first fluid outlet provided at the other end thereof, the first fluid inlet and the first fluid outlet being connected to each other via a first flow path extending in a straight line from the first fluid inlet to the first fluid outlet; and multiple tube sets accommodated inside the casing so that a fluid that flows through the interiors thereof undergoes heat exchange with a fluid that flows via the first flow path. The multiple tube sets are arrayed along the first flow path, and multiple U-shaped tubes constituting the tube sets are fixed only to a tube plate disposed parallel to the first flow path and located at both ends of the U-shaped tubes.

TECHNICAL FIELD

This application is based on Japanese Patent Application No.2011-274785, the contents of which are incorporated herein by reference.

The present invention relates to heat exchangers. More specifically, thepresent invention relates to a heat exchanger that is suitable as arepeater of a solar-heat gas turbine driven with a compressible workingfluid, such as air, heated by using sunlight.

BACKGROUND ART

Recently, in order to solve environmental problems, such as globalwarming, there is interest in natural energy, such as sunlight and windpower.

Accordingly, there have been proposals for solar-heat gas turbines thatare driven by generating a high-temperature, high-pressure compressibleworking fluid by means of solar heat by using sunlight, which is a typeof natural energy, and solar-heat gas-turbine power generating unitsthat generate power by driving a generator by means of such a solar-heatgas turbine.

Known examples of such a solar-heat gas turbine and a solar-heatgas-turbine power generating unit are disclosed in Patent Document 1.

CITATION LIST Patent Literature

-   {PTL 1}

Japanese Unexamined Patent Application, Publication No. 2010-281272

SUMMARY OF INVENTION Technical Problem

In a solar-heat gas turbine, the temperature of the interior of areheater that preheats a high-pressure compressible working fluidejected from a compressor through heat exchange with a high-temperaturecompressible working fluid discharged from a turbine becomes very highsince the high-temperature compressible working fluid discharged fromthe turbine passes through the interior. Thus, for example, when theheat exchanger disclosed in Japanese Unexamined Patent Application,Publication No. 2001-147093 is adopted as a reheater of a solar-heat gasturbine, thermal expansion of the U-shaped tubes 18 a in the lengthwisedirection is restrained by the U-shaped-tube fixing plate 19, possiblydamaging the U-shaped tubes 18 a.

The present invention has been made in view of the problem describedabove, and it is an object thereof to provide a heat exchanger thatpermits thermal expansion of U-shaped tubes in the lengthwise direction,thus serving to prevent damage to the U-shaped tubes, that causes lessheat dissipation, thus serving to improve the heat efficiency, that iseasy to inspect and repair, and that can produce compressed air withless pulsation of temperature.

Solution to Problem

In order to solve the problem described above, the present inventionemploys the following solutions.

A heat exchanger according to a first aspect of the present invention isa heat exchanger including a casing having a first fluid inlet providedat one end thereof and a first fluid outlet provided at the other endthereof opposite the one end, the first fluid inlet and the first fluidoutlet being connected to each other via a first flow path extending ina straight line from the first fluid inlet to the first fluid outlet;and multiple tube sets accommodated inside the casing so that a fluidthat flows through the interiors thereof undergoes heat exchange with afluid that flows via the first flow path, wherein the multiple tube setsare arrayed along the first flow path, and multiple U-shaped tubesconstituting the tube sets are fixed only to a tube plate disposedparallel to the first flow path and located at both ends of the U-shapedtubes.

In the heat exchanger according to the first aspect of the presentinvention, the U-shaped tubes are fixed only at a single side thereof totube holes that are provided in the tube plate and through which bothends of the U-shaped tubes are inserted.

Thus, thermal expansion of the U-shaped tubes in the lengthwisedirection is permitted, which serves to prevent damage to the U-shapedtubes.

Furthermore, in the heat exchanger according to the present invention,the first fluid inlet and the first fluid outlet are connected to eachother via a single path, namely, the first flow path extending in astraight line from the first fluid inlet to the first fluid outlet.

Thus, pressure loss in the first flow path can be reduced. Furthermore,it is possible to make a large amount of fluid flow via the first flowpath, which serves to improve the heat exchange efficiency.

In the above heat exchanger, more preferably, a partition plateseparating straight portions and turning portions of the U-shaped tubesis disposed parallel to the first flow path, and gaps are providedbetween the inner circumferential surfaces of tube holes that areprovided in the partition plate and through which the straight portionsof the U-shaped tubes are inserted and the outer circumferentialsurfaces of the U-shaped tubes.

In the heat exchanger constructed as described above, a space is formedoutside the first flow path by the partition plate and the casing,causing a portion of the fluid passing via the first flow path tostagnate in that space.

Thus, the fluid present in the space acts as a heat insulating layer.This serves to maintain the temperature of the fluid passing via thefirst flow path, which serves to improve the heat exchange efficiencyeven further.

In the above heat exchanger, more preferably, a header that communicatesbetween the outlet end of a tube set located on the upstream side andthe inlet end of a tube set located on the downstream side thereof isprovided.

In the heat exchanger constructed as described above, the fluid that hasundergone heat exchange with the fluid passing via the first flow pathwhile passing through a tube set located on the upstream side is guidedto the tube set located on the downstream side thereof so that the fluidthen undergoes heat exchange with the fluid passing via the first flowpath. This serves to improve the heat exchange efficiency even further.

In the above heat exchanger, more preferably, the U-shaped tubes arefixed to the tube plate by expanding the ends of the U-shaped tubesinserted through the tube holes.

In the heat exchanger constructed as described above, the ends of theU-shaped tubes are fixed to the tube plate just by tube expansion,without employing welding.

Thus, the combination of the material of the tube plate and the materialof the U-shaped tubes, which must be taken into account when welding,need not be considered here, allowing free choice of the material of thetube plate and the material of the U-shaped tubes.

A solar-heat gas-turbine power generating system according to a secondaspect of the present invention includes any one of the above heatexchangers as a repeater.

In the solar-heat gas-turbine power generating system according to thesecond aspect of the present invention, since the heat exchanger thatpermits thermal expansion of the U-shaped tubes in the lengthwisedirection, which serves to prevent damage to the U-shaped tubes, isincluded as the reheater, the reliability of the solar-heat gas-turbinepower generating system can be improved.

Furthermore, in the solar-heat gas-turbine power generating systemaccording to the present invention, since the heat exchanger having ahigh heat exchange efficiency is included as the reheater, it ispossible to further boost the temperature of the compressible workingfluid introduced into the turbine. This serves to improve the cycleefficiency of the heat cycle.

Advantageous Effects of Invention

According to the present invention, because the partition plates and thetubes are not joined together, thermal expansion of the U-shaped tubesin the lengthwise direction is permitted. Thus, an advantage is affordedin that damage to the U-shaped tubes can be prevented.

Furthermore, the space between the first partition plate and the casingserves as a stagnation region that is separated from the fluid path.Thus, an advantage is afforded in that the stagnation region exhibits aheat insulating effect, serving to reduce heat dissipation.

Furthermore, the header itself is designed to have a size large enoughfor a person to enter, a hatch for inspection work of thediameter-expanded joints with the tubes is provided at the header, and aladder is provided inside the header. This structure facilitatesinspection, making it easy to seal off a tube with a plug even if thetube is damaged, forming a perforation.

Furthermore, since multiple headers are provided in the middle of thetube path, the air whose temperature has been boosted by compression andthe air that has been further heated by the heat exchanger are mixed inthe headers, so that the temperature becomes uniform before it is fed tothe heat receiver. Thus, the air discharged from the heat receiverbecomes free of pulsation of temperature, so that the rotation rate ofthe turbine directly connected to the generator becomes free of minutefluctuations. Accordingly, an advantage is afforded in that power ofgood quality with extremely small frequency fluctuations can beobtained.

Furthermore, it is possible to pull out the headers and tube setswithout removing the casing, which facilitates replacement of tubes whenthe tubes become degraded.

Furthermore, since a gap is provided between tube sets, where the firstfluid becomes uniform, the temperature efficiency can be improved.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a construction diagram (system diagram) showing a specificexample of a case where a heat exchanger according to an embodiment ofthe present invention is used as a reheater for a solar-heat gas turbineand a solar-heat gas-turbine power generating unit.

FIG. 2 is a perspective view of the heat exchanger according to theembodiment of the present invention.

FIG. 3 is a sectional view of the heat exchanger according to theembodiment of the present invention.

DESCRIPTION OF EMBODIMENTS

Now, a heat exchanger according to an embodiment of the presentinvention, in particular, a heat exchanger that can be suitably used asa reheater of a solar-heat gas turbine that is driven by using acompressible working fluid, such as air, heated by using sunlight, willbe described with reference to FIGS. 1 to 3.

FIG. 1 is a construction diagram (system diagram) showing a specificexample of a case where the heat exchanger according to this embodimentis used as a reheater for a solar-heat gas turbine and a solar-heatgas-turbine power generating unit. FIG. 2 is a perspective view of theheat exchanger according to the embodiment. FIG. 3 is a sectional viewof the heat exchanger according to the embodiment.

As shown in FIG. 1, a solar-heat gas turbine GT includes, as its maincomponents, a compressor 1 that compresses a compressible working fluidto boost its pressure, a heat receiver 2 that heats the compressibleworking fluid with heat obtained by converting sunlight to boost itstemperature, and a turbine 3 that converts thermal energy possessed bythe high-temperature, high-pressure compressible working fluid intomechanical energy. That is, the solar-heat gas turbine GT includes theheat receiver 2 that heats the high-pressure compressible working fluidby using the thermal energy of sunlight to boost its temperature insteadof a combustor that combusts a fuel such as natural gas to generatehigh-temperature, high-pressure combustion gas.

The heat receiver 2 in this case is a device for converting sunlightinto thermal energy. With the heat receiver 2, it is possible to heat ahigh-pressure compressible working fluid to boost its temperature byusing the heat of light collected by a light concentrator (heliostat),which is not shown.

Furthermore, a solar-heat gas-turbine power generating unit thatgenerates electric power by using sunlight can be constructed byconnecting a generator 4 coaxially to the solar-heat gas turbine GT sothat the generator 4 is driven by the solar-heat gas turbine GT.

Furthermore, a reheater 5 preheats the high-pressure compressibleworking fluid whose pressure has been boosted by the compressor 1, byusing exhaust heat of the compressible working fluid that is dischargedfrom a chimney 6 into the air after performing work in the turbine 3.

The heat exchanger 10 according to this embodiment is a heat exchangerthat can be suitably used as the reheater 5 of the solar-heat gasturbine GT in particular. As shown in FIG. 2 or FIG. 3, the heatexchanger 10 includes a casing 11 and multiple (four in this embodiment)tube sets 12.

The casing 11 has a substantially rectangular parallelepiped or cubicexternal shape and accommodates the tube sets 12 inside. On the frontface of the casing 11, a first fluid inlet 21 is provided, which is anopening having a rectangular shape when viewed from the front andthrough which a high-temperature fluid (the high-temperaturecompressible working fluid discharged from the turbine 3) flows in. Onthe back face, a first fluid outlet 22 is provided, which is an openinghaving a rectangular shape when viewed from the back and through whichthe fluid that has undergone heat exchange inside the casing flows out.On a first face, a tube plate 23 is provided. Furthermore, the threefaces of the casing other than the front face, the back face, and thefirst face are closed off with a second face, a third face, and a fourthface surrounding the front and back faces together with the first face.

In the tube plate 23, multiple (672 in this embodiment) tube holes (notshown) are provided, through which both ends of multiple (336 in thisembodiment) U-shaped tubes 24 constituting the tube sets 12 areinserted.

The ends of the U-shaped tubes 24 inserted through the tube holes areexpanded by using a tool such as a mandrel, so that the U-shaped tubes24 are fixed to the tube plate 23 only on that single side.

The first fluid inlet 21 and the first fluid outlet 22 are connected toeach other via a first flow path 25 extending in a straight line fromthe first fluid inlet 21 to the first fluid outlet 22. A fluid thatflows in from the first fluid inlet 21 undergoes heat exchange with afluid that passes through the U-shaped tubes 24 (the high-pressurecompressible working fluid ejected from the compressor) and then flowsout from the first fluid outlet 22. The first flow path 25 is formed byfour faces, namely, the tube plate 23, the second face, a firstpartition plate (support plate) 26 disposed at the inner side of thethird face and parallel to the third face, and the fourth face.Furthermore, between the tube plate 23 and the first partition plate 26,a second partition plate (support plate) 27 and a third partition plate(support plate) 28 are disposed parallel to the tube plate 23 and thefirst partition plate 26, which separate the first flow path 25 intothree flow paths along the flow direction. In each of the firstpartition plate 26, the second partition plate 27, and the thirdpartition plate 28, multiple (672 in this embodiment) tube holes (notshown) are provided, through which the multiple U-shaped tubes 24constituting the tube sets 12 are inserted. The tube holes provided inthe first partition plate 26 and the second partition plate 27 have aninner diameter greater than the outer diameter of the U-shaped tubes 24so that thermal expansion of the U-shaped tubes 24 in the lengthwisedirection (lateral direction in FIG. 3) will not be restrained. The tubeholes provided in the third partition plate 28 disposed so as toseparate the straight portions and turning portions of the U-shapedtubes 24 have an inner diameter greater than the inner diameter of thetube holes provided in the first partition plate 26 and the secondpartition plate 27 so that thermal expansion of the U-shaped tubes 24 inthe lengthwise direction will not be restrained and so that a slightamount of the fluid that flows via the first flow path 25 flows into aspace S formed between the third partition plate 28 and the third face.

The space S is formed by the third partition plate 28, the second face,the third face, the fourth face, the front face except the area wherethe first fluid inlet 21 is formed, and the back face except the areawhere the first fluid outlet 22 is formed.

On the outer side of the tube plate 23, multiple headers, namely, threeheaders 31, 32, and 33 in this embodiment, are provided.

The first header 31 is a housing substantially having an external shapeof a cylinder cut into half with both ends closed. The first header 31guides the fluid that undergoes heat exchange with the fluid passing viathe first flow path 25 to the inlet end of the tube set 12 located onthe most upstream side via a second fluid inlet 34 and guides the fluidthat flows out from the outlet end of the same tube set 12 to the inletend of the tube set 12 located on the downstream side thereof. In thefirst header 31, a barrier wall 35 is provided to prevent mixing betweenthe fluid guided from the second fluid inlet 34 to the inlet end of thetube set 12 located on the most upstream side and the fluid that flowsout from the outlet end of the same tube set 12.

The second header 32 is a housing substantially having an external shapeof a cylinder cut into half with both ends closed. The second header 32guides the fluid that flows out from the outlet end of the tube set 12located second from the upstream side to the inlet end of the tube set12 located on the downstream side thereof.

The third header 33 is a housing substantially having an external shapeof a cylinder cut into half with both ends closed. The third header 33guides the fluid that flows out from the outlet end of the tube set 12located third from the upstream side to the inlet end of the tube set 12located on the downstream side thereof and guides the fluid that flowsout from the outlet end of the same tube set 12 to the outside via asecond fluid outlet 36. In the third header 33, a barrier wall 37 isprovided to prevent mixing between the fluid guided to the inlet end ofthe tube set 12 located fourth from the upstream side and the fluid thatflows out from the outlet end of the same tube set 12.

In each of the tube sets 12, multiple (four in this embodiment) U-shapedtubes 24 having straight portions of the same length and turningportions with different radii are laid out within the same plane suchthat the U-shaped tubes 24 having smaller radii are disposed at theinner side and the U-shaped tubes 24 having greater radii are disposedat the outer side, and multiple (21 in this embodiment) sets of thisarrangement are arrayed so as to be stacked in the directionperpendicular to this plane.

A certain gap is provided between the U-shaped tubes 24 laid out withinthe same plane and between the U-shaped tubes 24 stacked in thedirection perpendicular to the plane, so that the fluid that flows fromthe first fluid inlet 21 toward the first fluid outlet 22 passes throughthese gaps.

Furthermore, reference sign 38 in FIG. 3 denotes a hatch for inspectionwork.

In the heat exchanger 10 according to this embodiment, the U-shapedtubes 24 are fixed only at a single side thereof to the tube holesprovided in the tube plate 23, through which both ends of the U-shapedtubes 24 are inserted.

This permits thermal expansion of the U-shaped tubes 24 in thelengthwise direction, which serves to prevent damage to the U-shapedtubes 24.

Furthermore, in the heat exchanger 10 according to this embodiment, thefirst fluid inlet 21 and the first fluid outlet 22 are connected to eachother via a single path, namely, the first flow path 25 extending in astraight line from the first fluid inlet 21 to the first fluid outlet22.

Thus, pressure loss in the first flow path 25 can be reduced.Furthermore, it is possible to make a large amount of fluid flow via thefirst flow path 25. This serves to improve the heat exchange efficiency.

Furthermore, in the heat exchanger 10 according to this embodiment, thespace S is formed by the first partition plate 26 and the casing 11outside the first flow path 25. The fluid passing via the first flowpath 25 flows into this space S via the gaps provided between the innercircumferential surfaces of the tube holes and the outer circumferentialsurfaces of the U-shaped tubes 24, causing a portion of the fluid thatpasses via the first flow path 25 to stagnate in the space S.

Thus, the fluid present in the space S acts as a heat insulating layer.This serves to maintain the temperature of the fluid passing via thefirst flow path 25, which serves to improve the heat exchange efficiencyeven further.

Furthermore, in the heat exchanger 10 according to this embodiment, thefluid that has undergone heat exchange with the fluid passing via thefirst flow path 25 while passing through a tube set 12 located on theupstream side is guided to the tube set 12 located on the downstreamside thereof so that the fluid then undergoes heat exchange with thefluid passing via the first flow path 25. This serves to improve theheat exchange efficiency even further.

Furthermore, in the heat exchanger 10 according to this embodiment, theends of the U-shaped tubes 24 are fixed to the tube plate 23 just bytube expansion, without employing welding.

Thus, the combination of the material of the tube plate 23 and thematerial of the U-shaped tubes 24, which must be taken into account whenwelding, need not be considered here, allowing free choice of thematerial of the tube plate 23 and the material of the U-shaped tubes 24.

Since the solar-heat gas turbine GT according to this embodimentincludes, as the reheater 5, the heat exchanger 10 that permits thermalexpansion of the U-shaped tubes 24 in the lengthwise direction, whichserves to prevent damage to the U-shaped tubes 24, the reliability ofthe solar-heat gas turbine GT can be improved.

Furthermore, since the solar-heat gas turbine GT according to thisembodiment includes, as the reheater 5, the heat exchanger 10 having ahigh heat exchange efficiency, it is possible to further boost thetemperature of the compressible working fluid introduced into theturbine 3. This serves to improve the cycle efficiency of the heatcycle.

The present invention is not limited to the embodiment described above,and suitable modifications and alternatives may be introduced as needed.

For example, although the above-described embodiment includes the fourtube sets 12 as a specific example, the present invention is not limitedto this embodiment, and the number of tube sets included may be two,three, or five or more.

Furthermore, although the second fluid outlet 36 is provided at thefirst fluid inlet 21 side, and the second fluid inlet 34 is provided atthe first fluid outlet 22 side in the above-described embodiment, thepresent invention is not limited to this embodiment, and the secondfluid inlet 34 may be provided at the first fluid inlet 21 side, and thesecond fluid outlet 36 may be provided at the first fluid outlet 22side.

REFERENCE SIGNS LIST

-   1 Compressor-   3 Turbine-   5 Reheater-   10 Heat exchanger-   11 Casing-   12 Tube sets-   21 First fluid inlet-   22 First fluid outlet-   23 Tube plate-   24 U-shaped tubes-   25 First flow path-   26 First partition plate (partition plate)-   31 First header (header)-   32 Second header (header)-   33 Third header (header)-   GT Solar-heat gas turbine

1. A heat exchanger comprising: a casing having a first fluid inletprovided at one end thereof and a first fluid outlet provided at theother end thereof opposite the one end, the first fluid inlet and thefirst fluid outlet being connected to each other via a first flow pathextending in a straight line from the first fluid inlet to the firstfluid outlet; and multiple tube sets accommodated inside the casing sothat a fluid that flows through the interiors thereof undergoes heatexchange with a fluid that flows via the first flow path, wherein themultiple tube sets are arrayed along the first flow path, and multipleU-shaped tubes constituting the tube sets are fixed only to a tube platedisposed parallel to the first flow path and located at both ends of theU-shaped tubes.
 2. A heat exchanger according to claim 1, wherein apartition plate separating straight portions and turning portions of theU-shaped tubes is disposed parallel to the first flow path, and gaps areprovided between the inner circumferential surfaces of tube holes thatare provided in the partition plate and through which the straightportions of the U-shaped tubes are inserted and the outercircumferential surfaces of the U-shaped tubes.
 3. A heat exchangeraccording to claim 1, wherein a header that communicates between theoutlet end of a tube set located on the upstream side and the inlet endof a tube set located on the downstream side thereof is provided.
 4. Aheat exchanger according to claim 1, wherein the U-shaped tubes arefixed to the tube plate by expanding the ends of the U-shaped tubesinserted through the tube holes.
 5. A solar-heat gas-turbine powergenerating system comprising a heat exchanger according to claim 1 as arepeater that preheats a high-pressure compressible working fluidejected from a compressor through heat exchange with a high-temperaturecompressible working fluid discharged from a turbine.